The invention concerns a filter element, in particular for filtration of fluids of internal combustion engines, for example, intake air, lubricant oil, fuel or urea-water solution, a method for its production, and the use of a hot melt for gluing filter elements.
DE 1299230 discloses a filter whose folds are connected by means of individual hot melt dots.
In such filter elements there is the problem that upon application of the hot melts, in particular for a bead-like application with elongate hot melt beads or for dot-shaped application, for example, by means of applicator nozzles, applicator rollers etc., hot melt strings are formed between the application equipment and the ends of the hot melt beads; they quickly cool down and harden and remain on the filter in the application area. The problem occurs particularly frequently upon closing the applicator nozzles. This can be particularly disadvantageous in case of an adhesive connection at the clean side of the filter element because in operation pieces of cold hot melt strings may become detached and entrained by the fluid flow. This can be disadvantageous in particular in the filtration of intake air of internal combustion engines.
For gluing zigzag-shaped folded filter elements hot melts are used regularly. Non-reactive hot melts are products which are free of solvent and at room temperature are more or less solid and in the hot state are applied onto a surface to be glued and produce upon cooling the adhesive connection. This group of adhesives is also known as hot melt and is based on various chemical raw materials. DIN EN 923 defines hot melt as a thermally meltable adhesive system that after cooling develops cohesion. Melting points are usually between 80° C. and 250° C. From the prior art various non-reactive hot melts on the basis of polyesters or polyamides are known, for example, Macromelt 2030, 6208 from Henkel, WEVO T 570, P 165 from WEVO Chemie, or TH 207, TH 111 from Bostik. From Müller and Rath, Formulierung von Kleb- and Dichtstoffen, Hannover: Vincentz Network, 2004, further hot melts are known. Upon application of the hot melts, in particular upon interrupting the application by means of applicator nozzles, hot melt strings are produced regularly which form between the applied adhesive and an applicator nozzle and optionally may tear off (stringing).
The invention has the object to provide a filter element, glued by means of a hot melt with a reduced amount of hot melt strings, and a method for its production.